Process for producing titanium-containing silicon oxide catalyst, the catalyst, and process for producing oxirane compound with the catalyst

ABSTRACT

A process for producing a titanium-containing silicon oxide catalyst having a silicon-carbon-silicon bond, silicon-oxygen-silicon bond and silicon-oxygen-titanium bond which includes causing a silicon compound of the following formula (1) and a titanium alkoxide compound to gel in a water and/or alcohol solvent and removing the solvent in the resulted gel by extraction with a supercritical fluid 
                 
 
(R 1  to R 7  each independently represent a hydrocarbon group having 1 to 20 carbon atoms.).

TECHNICAL FIELD

The present invention relates to a process for producing atitanium-containing silicon oxide catalyst, said catalyst and a processfor producing an oxirane compound using the catalyst. More particularly,the present invention relates to a process for producing atitanium-containing silicon oxide catalyst by which an oxirane compoundcan be obtained under high selectivity and yield by reacting an olefinand a hydroperoxide compound in the presence of said catalyst, saidcatalyst and a process for producing an oxirane compound using thecatalyst.

BACKGROUND ART

Methods of obtaining an oxirane compound by reacting an olefin and ahydroperoxide compound in the presence of a catalyst are publicly known.For example, U.S. Pat. No. 4,367,342 discloses a process for using atitanium-supported silica catalyst. However, conventional methods areinsufficient from the standpoints of selectivity to a oxirane compoundas an objective compound and yield thereof.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a process for producinga titanium-containing silicon oxide catalyst by which an oxiranecompound can be obtained with high selectivity and yield by reacting anolefin and a hydroperoxide compound in the presence of said catalyst,said catalyst and a process for producing an oxirane compound using thecatalyst.

Namely, the present invention relates to a process for producing atitanium-containing silicon oxide catalyst having asilicon-carbon-silicon bond, silicon-oxygen-silicon bond andsilicon-oxygen-titanium bond, which comprises causing a silicon compoundof the following formula (1) and a titanium alkoxide compound to a gelin a water and/or alcohol solvent and removing the solvent in theresulted gel by extraction with a supercritical fluid:

(wherein, R¹ to R⁷ each independently represent a hydrocarbon grouphaving 1 to 20 carbon atoms.).

Further, another invention relates to a process for producing an oxiranecompound, comprising reacting an olefin with a hydroperoxide compound inthe presence of a catalyst obtained by the above-mentioned process.

BEST MODE FOR CARRYING OUT THE INVENTION

In the process for producing a titanium-containing silicon oxidecatalyst of the present invention, silicon compounds of the followingformula (1) (hereinafter, referred to as silicon compound (1)) are used:

(wherein, R¹ to R⁷ each independently represent a hydrocarbon grouphaving 1 to 20 carbon atoms.).

Preferably, R¹ to R⁶ represent an alkyl group, and a methyl group, ethylgroup, propyl group, butyl group, isopropyl group, isobutyl group andthe like are exemplified, and particularly preferable are a methyl groupand an ethyl group which are easily available industrially.

R⁷ represents a divalent hydrocarbon group having 1 to 20 carbon atoms,and examples thereof include alkylene groups such as a methylene group,ethylene group, propylene group, butylenes group and the like, aromatichydrocarbon groups such as a phenylene group,1,4-bis(methylene)phenylene group, 1,4-bis(ethylene)phenylene group andthe like, further, hydrocarbon groups obtained by combining them, andparts of these hydrocarbon groups may be substituted with hetero atoms.

Preferable specific examples of the silicon compound (1) includebis(triethoxysilyl)ethane, bis(triethoxysilyl)methane,bis(trimethoxysilyl)ethane, bis(trimethoxysilyl)methane,bis(trimethoxysilyl)hexane, 1,4-bis(trimethoxysilylethyl)benzene and thelike.

In the present invention, it is preferable to use a silicon compound ofthe following formula (2) (hereinafter, referred to as silicon compound(2)) and/or a silicon compound of the following formula (3)(hereinafter, referred to as silicon compound (3)) in addition to thesilicon compound (1) from the standpoint of controllability of skeletonstrength and hydrophobicity to any degrees.Si(OR⁸)₄  (2)(R⁹)_(m)Si(OR¹⁰)_(4-m)  (3)(R⁸, R⁹ and R¹⁰ each independently represents a hydrocarbon group having1 to 20 carbon atoms. m represents an integer of 1 or 2. When aplurality of R⁸'s, R⁹'s or R¹⁰'s are present, they may be the same ordifferent.).

Preferably, examples of the hydrocarbon group include alkyl groupshaving 1 to 20 carbon atoms such as a methyl group, ethyl group, propylgroup, isopropyl group, butyl group and the like, aryl groups having upto 20 carbon atoms such as a phenyl group and the like, aralkyl groupshaving up to 20 carbon atoms such as a benzyl group an the like, andparts of these hydrocarbon groups may be substituted by hetero atoms.Particularly preferable are a methyl group, ethyl group, propyl group,butyl group and phenyl group which are easily available industrially.

Preferable specific examples of the silicon compound (2) includetetramethoxysilane, tetraethoxysilane, tetrapropoxysilane,tetraisopropoxysilane, tetrabutoxysilane and the like. Preferablespecific examples of the silicon compound (3) includetrimethoxymethylsilane, trimethoxyphenylsilane, dimethoxydimethylsilane,triethoxymethylsilane, triethoxyphenylsilane and the like.

The ratio of the molar amount of hydrocarbon groups bonded to a siliconatom to the total silicon molar amount of the silicon compound (1), andsilicon compound (2) and/or silicon compound (3) is preferably from 5 to150%, further preferably from 2.0 to 80%. When the ratio is too small,the catalytic performance may be decreased, on the other hand, when toolarge, gellation may not progress in catalyst synthesis.

As the titanium alkoxide compound, tetramethoxytitanium,tetraethoxytitanium, tetrapropoxytitanium, tetraisopropoxytltanium,tetrabutoxytitanium, diisopropoxybisacetylacetonatotitanium and the likeare exemplified.

The use amount used (molar amount) of the titanium alkoxide compound ispreferably from 0.0001 to 1 based on the total molar amounts of allsilicon compounds. When the use amount of the titanium alkoxide compoundis too small, the activity may become low because of decrease of activepoints, on the other hand, when too large, the activity may become lowbecause of production of titania.

As the solvent alcohol, methanol, ethanol, n-propanol, isopropanol,butanol, cyclohexanol, ethylene glycol and the like are exemplified.

In the present invention, a silicon compound and a titanium alkoxidecompound are gelled in a water and/or alcohol solvent. As the gellingmethod, the following methods are mentioned. Namely, hydrolysis andcondensation reaction of a silicon compound and titanium compound areprogressed by adding usually an acid or alkaline as a promoter into anaqueous and/or an alcoholic solution containing a silicon compound andtitanium compound dissolved, to obtain gel which is a polymericcondensate having a silicon-carbon-silicon bond, silicon-oxygen-siliconbond and silicon-oxygen-titanium bond. The gelling reaction is usuallyconducted at from −30 to 100° C. Aging may also be conducted for growthof gelled solid. Aging is usually conducted at from 0 to 200° C. for 180hours or less. As the above-mentioned promoter for hydrolysis andcondensation reaction, an acid or an alkaline is used, and use of anacid is preferable from the standpoint of the resulting catalyticperformance. Examples of the acid include inorganic acids such as nitricacid, hydrochloric acid, sulfuric acid and the like and organic acidssuch as formic acid, acetic acid and the like, and examples of thealkaline include sodium hydroxide, potassium hydroxide, ammonia and thelike. The added amount of the acid or alkaline can not be restrictedsince it depends on the kinds and gelling conditions of raw materialcompounds, and usually in the range from 0.0001 to 100 mol permol of thesilicon compound.

A solvent in the resulted gel is removed by extraction withsupercritical fluid. As the fluid, carbon dioxide, methanol, ethanol,propanol and the like are exemplified, and use of carbon dioxide ispreferable since post treatment is easy and a high catalytic performanceis obtained. As the method of extraction, the following are mentioned.That is, the supercritical extraction can be carried out underconditions for forming supercritical carbon dioxide in an autoclavecharged with gel, namely, by flowing supercritical carbon dioxide at atemperature of about 31° C. or more under a pressure of about 7.3 MPa ormore. For example, supercritical carbon dioxide fluid having atemperature of 31 to 100° C. and a pressure of 10 to 30 MPa can be used.By this procedure, water and/or an alcohol solvent incorporated in gelcan be removed by extraction. In extraction removal, it is necessary touse supercritical fluid. By this process, porosity which is preferablefor a catalyst can be obtained.

In the present invention, after the supercritical extraction operation,the product can be dried and further subjected to silylation treatment.The drying can be carried out at from 0 to 200° C. under reducedpressure or under a stream of air, nitrogen or the like. The silylationtreatment is conducted by contacting a dried catalyst obtained in theformer step with a silylating agent in a solvent or gas phase at atemperature from 20 to 300° C. to convert a hydroxyl group present onthe surface of a catalyst into a silyl group. By performing thissilylation treatment, a catalytic performance can be improved. Examplesof the silylating agent include organosilanes such aschlorotrimethylsilane, dichlorodimethylsllane, chlorotriethylsilane andthe like, organosilylamines such as N-trimethylsilylimidazole,N-t-butyldimethylsllylimidazole, N-trimethylsilyldimethylamine and thelike, organosilylamides such as N,O-bistrimethylsilylacetamide,N-trimethylsilylacetamide and the like, organosilazanes such ashexamethyldisilazane, heptamethyldisilazane and the like.Hexamethyldisilazane is a preferable silylating agent.

The catalyst of the present invention is a titanium-containing siliconoxide catalyst having a silicon-carbon-silicon bond,silicon-oxygen-silicon bond and silicon-oxygen-titanium bond. Thesilicon-carbon-silicon bond in the catalyst can be confirmed mainly by²⁹Si-NMR and ¹³C-NMR. For example, when two Si atoms are crosslinkedthrough a phenyl group, carbon number of a phenyl group bonded to Si canbe confirmed by two peaks near 145 ppm by ¹³C-NMR, and presences of Siand Si atom bonded to C can be confirmed by three peaks appearing near−60 ppm to −80 ppm by ²⁹Si-NMR. Details thereof are described in aliterature of Douglas A. Loy, Kenneth J. Shea, et al. (J. Am. Chem. Soc.1992, 114, 6700, J. of Non-Crystalline Solids 1993, 160, 234) and thelike. Further, the state of titanium present in the catalyst can beconfirmed by a UV spectrometer or the like. Existence of an absorptionband near 200 to 230 nm indicates a titanium atom present in highlydispersed condition in silica. On the other hand, when titaniumcompounds are mutually condensed to give poorly dispersed state, anabsorption band appears characteristically in a region of 300 nm ormore.

The catalyst obtained in the present invention can be used in selectiveoxidation reactions, for example, an olefin epoxidation reaction, andadditionally, various oxidation reactions of organic compounds, sincethe catalyst has large surface area and highly dispersed titanium activesites. If desired, it is also possible to reinforce acid sites of thecatalyst by addition of a third component such as alumina or the like,and the catalyst can be used also in an alkylation reaction, catalyticreforming reaction and the like.

The catalyst of the present invention is optimally used in a process forproducing an oxirane compound, comprising reacting an olefin and ahydroperoxide compound.

As the olefin subjected to the reaction, exemplified are ethylene,propylene, 1-butene, 2-butene, isobutylene, butadiene, 1-pentene,isoprene, 1-hexene, 1-octene, 1-decene, cyclopentene, cyclohexene,styrene, allyl chloride, allyl alcohol and the like.

As the hydroperoxide compound subjected to the reaction, any of organichydroperoxides and inorganic hydroperoxides can be used. As the organichydroperoxide, ethylbenzene hydroperoxide, cumene hydroperoxide, t-butylhydroperoxide and the like are exemplified. As the inorganichydroperoxide, hydrogen peroxide and the like are exemplified.

From the industrial viewpoint, a process for producing propylene oxidefrom propylene and organic hydroperoxide is important, and the catalystof the present invention can be used suitably in this reaction.

The reaction is carried out in liquid phase in the presence or absenceof a suitable solvent. As the solvent, compounds which are inert to thereaction and abundant in solubility of an olefin and/or hydroperoxidecompound can be used. Specific examples of a solvent when an organichydroperoxide is used include hydrocarbons such as butane, octane,benzene, toluene, ethylbenzene, cumene and the like. On the other hand,specific examples of a solvent when an inorganic hydroperoxide is usedinclude methanol, ethanol, isopropanol, t-butanol, water and the like.

The epoxidation reaction can be conducted generally at temperatures from0 to 200° C. The pressure may be such extent as to keep a reactionmixture in liquid condition, and generally from 0.1 to 10 MPa. Theepoxidation reaction uses a powder catalyst or molded catalyst and canbe carried out in a slurry or fixed bed according to a batch-wisemethod, semi-continuous method or continuous method.

EXAMPLES

Next, the present invention are illustrated by Examples.

Example 1

Into a 300 ml flask was charged 32.1 g of1,4-bis(trimethoxysilylethyl)benzene, 2.31 g of tetra-n-butoxytitaniumand 65 ml of n-propanol. A mixed solution of 23 ml of 70% nitric acidand 35 ml of n-propanol was added from a dropping funnel into thissolution over about 1 hour while stirring at 25%. This solution wasallowed to stand at 25° C. for 20 days to obtain gel. The resulted gelwas transferred into an autoclave, and a solvent in the gel was removedby extraction by flowing supercritical carbon dioxide of 45° C. and 24MPa at a velocity of 8 g/min. for about 12 hours. Subsequently, theproduct was dried under reduced pressure at 25° C. and about 100 Pa for10 hours to effect silylation treatment, obtaining about 12 g of acatalyst. The resulted catalyst had a surface area of 384 m²/g and apore volume of 1.4 ml/g.

The epoxidation reaction test was carried out under the followingconditions. Into an autoclave was charged about 1 g of theabove-mentioned catalyst, 17 g of propylene and 24 g of a 35% solutionof ethylbenzene hydroperoxide in ethylbenzene, and they were reacted for1.5 hours at 80′ while stirring. The reaction solution was analyzed andthe reaction result was determined. The results are shown in Table 1.

Example 2

The same operation as in Example 1 was conducted except that 21.6 g of1,4-bis(trimethoxysilylethyl)benzene and 5.9 g ofdimethoxydimethylsilane were used as silicon compounds and 21 ml of 70%nitric acid was used. The results are shown in Table 1.

Example 3

The same operation as in Example 1 was conducted except that 16.2 g of1,2-bis(trimethoxysilyl)ethane and 6.2 g of dimethoxydimethylsilane wereused as silicon compounds and 21 ml of 70% nitric acid was used. Theresults are shown in Table 1.

Example 4

The same operation as in Example 1 was conducted except that 28.0 g of1,6-bis(trimethoxysilyl)hexane was used as a silicon compound and 5.7 mlof 70% nitric acid was further used. The results are shown in Table 1.

Comparative Example 1

The same operation as in Example 1 was conducted except that 26.1 g oftetramethoxysilane was used as a silicon compound and 30 ml of 70%nitric acid was used. The results are shown in Table 2.

Comparative Example 2

The same operation as in Example 1 was conducted except that 10.4 g oftetramethoxysilane and 14 g of trimethoxymethylsilane were used assilicon compounds and 26 ml of 70% nitric acid was used. The results areshown in Table 2.

The results indicate the following matters. All examples satisfying theconditions of the present invention show satisfactory reaction results.On the other hand, Comparative Example 1 and Comparative Example 2 whichdid not use the silicon compound (1) of the present invention are poorin reaction results.

TABLE 1 Example 1 2 3 4 Ratio of R (%) 50 95 95 50 Reaction result EBHPconversion (%) 97.4 87.5 97.4 91.1 PO/C3′ yield (%) 97.5 96.2 97.6 97.8

TABLE 2 Comparative xample 1 2 Ratio of R (%) 0 60 Reaction result EBHPconversion (%) 81.0 38.3 PO/C3′ yield (%) 90.2 98.0Explanation of Tables

Ratio of R (%): Ratio of the total molar amount of hydrocarbon groups Rbonded to a Si atom to the total molar amount of Si.

EBHP conversion (%): [reacted EBHP (ethylbenzene hydroperoxide)/fedEBHP]×100(%).

PO/C3′ yield (%): [produced PO (propylene oxide) (mol)/reacted propylene(mol)]×100 (%).

INDUSTRIAL APPLICABILITY

As described above, the present invention can provide atitanium-containing silicon oxide catalyst which can give an oxiranecompound under high selectivity and yield by reacting an olefin and ahydroperoxide compound, and a process for producing an oxirane compoundusing the catalyst.

1. A process for producing a titanium-containing silicon oxide catalysthaving a silicon-carbon-silicon bond, silicon-oxygen-silicon bond andsilicon-oxygen-titanium bond, which comprises contacting a siliconcompound of formula (1) and a titanium alkoxide compound in water and/oralcohol solvent and removing the solvent in the resulted gel byextraction with a supercritical fluid:

(wherein, R¹ to R⁷ each independently represent a hydrocarbon grouphaving 1 to 20 carbon atoms).
 2. The process according to claim 1,further comprising a silicon compound of the following formula (2)and/or a silicon compound of the following formula (3)Si(OR⁸)₄  (2)(R⁹)_(m)Si(OR¹⁰)_(4-m)  (3) (R⁸, R⁹ and R¹⁰ each independently representa hydrocarbon group having 1 to 20 carbon atoms. m represents an integerof 1 to
 2. When a plurality of R⁸'s, R⁹'s or R¹⁰'s are present in thesilicon compound (2) and the silicon compound (3), they may be the sameor different).
 3. The process according to claim 2, wherein the ratio ofthe molar amount of hydrocarbon groups bonded to a silicon atom to thetotal silicon molar amount of the silicon compound (1) and siliconcompound (2) and/or silicon compound (3) is from 5 to 150%.
 4. Atitanium-containing silicon oxide catalyst obtained by the processaccording to any of claims 1 to
 3. 5. A process for producing an oxiranecompound, comprising contacting an olefin with a hydroperoxide compoundand the catalyst of claim 4.